[Cryptic heterokaryons in strains of Saccharomyces cerevisiae. Conditions for detecting a cryptic nucleus].

A phenomenon discovered earlier, cryptic heterokaryosis in Saccharomyces yeast, has been further investigated. A phenotypically silent nucleus in a yeast cell may resume its expression after fusion with another parental cell. The resulting hybrid is capable of sporulation. By the growth of a cytoductant with an expressing nucleus from one parent and a silent nucleus from the other parent on suitable selective media, the silent nucleus can be activated. The presence of deletion or insertion mutations in several genes in YPH strains allows nuclei of the YPH type to be traced not only genetically but also by blotting.